Gas turbine rotor systems include successive rows of blades, which extend from respective rotor disks that are arranged in an axially stacked configuration. The rotor stack may be assembled through a multitude of systems such as fasteners, fusion, tie-shafts and combinations thereof.
Gas turbine rotor systems operate in an environment in which significant pressure and temperature differentials exist across component boundaries which primarily separate a core gas flow path and a secondary cooling air flow path. For high-pressure, high-temperature applications, the components experience thermo-mechanical fatigue (TMF) across these boundaries. Although resistant to the effects of TMF, the components may be of a heavier-than-optimal weight for desired performance requirements.
Increasing high pressure compressor (HPC) pressure ratio, and by extension, the overall engine pressure ratio (OPR), has been shown to improve overall engine cycle efficiency. One result of the higher OPR is an increase in the HPC discharge air temperature. At very high OPR, the temperature exiting the HPC may exceed the allowable metal temperatures of HPC disk alloys. Maintaining a light-weight, high efficiency engine includes cooling the HPC disks to keep the temperature in the disk material's region of high strength.
However, cooling discretely bladed disks and drums, or integrally bladed rotors (IBRs), is hampered by the relative surface area exposed to the hot HPC core gas flow path, versus the internal surface area exposed to the secondary cooling air flow path.